Process for the prevention of foaming in steam boilers



Patented Oct. 14, 1947 S PATENT OFFICE PROCESS FOR, THE PREVENTION or" FOAMING IN STEAM nomnas Arthur L. Jacoby, Western Springs, 111., assignor to National Aluminate Corporation, Chicago, 111., a corporation of Delaware No Drawing. Application March 27, 1942,

- SerialNo. 436,494

The present invention relates to antiioaming compositions which are used in steam boilers and similar steam generators, evaporators. etc.,- to overcome the tendency of the water therein to foam and hence to bring about the priming of the steam generator or the like.

One of the objects of the present invention relates to a liquid suitable for the generation of steam in steam generators and comprising water containing dissolved therein a very small quantity of" an acyl derivative of piperazine.

These acyl derivatives of piperazine are characterized by having a high molecular weight;

andwhen water containing these materials is heated to the boiling point in a steam boiler or other generator, being thereby evaporated, the concentration of solids therein will not bring about excessive foaming and the resulting priming. These compounds, moreover, are substantially nonvolatile with the steam and stable, so

that they will be retained by the water and neither they nor their decomposition products will appear in the steam and the resulting condensation products thereof.

It is well known in the operation of steam boilers-such as in electric power plants, railroad locomotives and the like, or in evaporators, that the water therein, even though initially it shows very little tendency to foam, will, when the amount of total solids therein approaches a relatively high concentration, develop a very decided tendency to foam. When this occurs, considerable quantities of, water are physically carried out of the boilers or evaporators with the steam, thus appearing in the steam lines and in the eventual condensate. Such priming has many disadvantages because it tends to contaminate the steam lines, to plug or corrodethe valves, and under serious conditions may even impair the cylinders and piston rods of the steam engines, or. the impeller blades of turbines in which the steam is used for the generation of power, Attempts have been made in the past to control this foaming, either by excessive blowdown of the boilers or by the injection thereinto of such materials as castor oil, tallow, and the like. While these fatty materials have some small degree of eillciency, they are, on the other hand, quite deficient in that they introduce new difllculties which, in some instances, are worse than the conditions they are intended to cure. In the first place, these fatty acids or glycerides are unstable under the conditions existing in the boilers, particularly as the pressure and temperature increase, the high temperatures leading to 6 Claims. ((51. 252-321) v 2 rapid decomposition of the glycerides, which, if anything, will tend to increase the foaming and priming difllculties. Furthermore, in many instances certain of the decomposition products thus produced, or sometimes even the materials themselves, have a definite volatility with steam and will, therefore, steam-distill out of' the boilers, thus/appearing in the steam and in the condensate. This, of course, is also very undesirable. Furthermore; such types of antifoaming agents usually have to be employed in relatively large quantities, adding not only to the expense but also to the inconvenience of operating the steam generators; and those which have a tendency to decompose do so quite rapidly, and hence their effectiveness is of short duration, which therefore necessitates the continual charging into the boilers or other 'steam generators of definite amounts of these older antifoaming agents. Moreover, such antifo'aming agents are difficult to use because the amounts in which they are efllcacious are very critical, and any overdosage usually aggravates the 'difilculty instead of curing it Applicant has now discovered, however, that thereis a series of compounds, which may be broadly designated as acyl derivatives of piperazine, which are of a high order of efficiency when used as an antifoaming and antipriming agent in steam generators. These acyl derivatives of piperazine must, however, be of high molecular weight and should possess certain limiting characteristics as regards molecular size, as hereinafter more fully discussed.

The materials of this invention may be broad ly described as mono ordiacyl derivatives of piperazine, wherein the acyl groups are derived from aliphatic carboxylic acids, aromatic carboxylic acids or arylsulfonic acids. These compounds, for the purposes of discussion, may conveniently be represented by the probable structural formula:

in which X is the hydrocarbon radical of an ali phatic carboxylic acid which may contain one or more double bonds and may contain hydroxyl groups, that is, XCO is the acyl radical of an aliphatic or hydroxyaliphatic acid; and Z is hydrogen: or the acyl radical of an aliphatic carboxylic acid, an aromatic carboxylic acid, or an arylsulfonic acid.

- It is to be understood that the formulas recited in theclaims are probable in that the formulas given are believed to he possessed bythe compoundsdisclosed, or whose method of preparation is disclosed in this specification.

Certain limitations as to the molecular size or the materials are known to exist, and for the sake of convenience, these will be discussed by reference to four classifications into which the materials of the invention may be grouped.

' First, there is'the group consisting of monoecyl pipera'zines, in which the single acyl radical is derived from a high-molecular-weight fatty acid. In this group, the total number of carbon atoms in the derivative should be at least about 24, that is, the fatty acid a'cyl radical should contain at least about 20 carbon atoms. An example of a compound falling in this group is the product resulting from the condensation of about one moi of erucic acid and one mol of plperazine'. Second, there is a group consisting'of diacyi piperazines, in which both acyl groups are de- I I Third, there isa group consisting of diacyl plperazines in which both acyl-groups are derived from fatty acids, but where the two groups differ widely from each other in respectto the number of carbon atoms in each. In this group, the total number of carbon atoms in' the derivative must be at least about 22. Some examples of mem- C. for about 3 hours. when cool, the product was a tan wax.

'Erample-zefiommercial stearic acid, having a mean molecular weight of about 269, was employed in this preparation. 16 grams (0.06 mol) .of the acid and 5.8 grams (0.03 mol) of piperazine hexahydrate were mixed and heated carefully to expel the most of the water. Then the mixture was stirred 2.5 hours at 150-160 C. When cool, the product was a brown wax.

Example 3.--A mixture of 8.1 grams (0.03 mol) of the stearicacid of Example 2 and 5.8 grams (0.03 mol) of piperazine hexahydrate was heated carefully to expel water and then stirred 2 hours at 150-160' G. Then 2.36 grams (0.03 mol) of acetyl chloride was added and allowed to react 15 minutes. when cool, the product was a brown wax.

bers of this group would include acetylstearyl-- piperazine and butyrylerucylpiperazine.

The fourth group consists of diacyl piperazines in which one acyl radical is derived from a fatty acid and the other acyl radical is that of anaromatic carboxylic or an arylsulfonic acid. In this group, the fatty acid acyl radical should contain at least about 16 carbon atoms, regardless of the size of the other acyl radical.

The term high molecular weight? derivative as used in the claims refers to compounds in M acid and acetyl chloride in turn; (7) stearic acid and benzoyl chloride in turn: (8) stearic acid and p-toluenesulfonyl chloride in turn; (9) oleic acid and acetyl chloride in turn; and (10) erucic acid.

It is possible to eflect acylation of piperazine by the use of an acid, the corresponding acid halide, and even the ester of the acid, as for.

example, glyceride, depending upon the conditions chosen for the process. The invention should-not be limited, therefore, by the following examples, which are merely intended to illustrate some satisfactory procedures for preparing a few of the materials within the scope of the present invention.

Erample 1.-A mixture of" 5.8 grams (0.03

'mol) of piperazine hexahydrate and 15.4 grams.

(0.06-mo1) of palmitic acid was heated carefully until most of the water had been expelled and irothing ceased. Then it was stirred at USO-160 which the number of carbon atoms corresponds Example 4.-8.1 grams (0.03 mol) of the stearic acid of Example 2, 5.8 grams (0.03 mol) of piperazine hexahydrate, and 4.2 grams (0.03-mol) of benzoyl chloride were condensed by the same .procedure as outlined in Example 3. When cool,

the product was a dark brown wax.

Emample 5..-8.1 grams (0.03 mol) of the stearic acid of Example 2, 5.8 grams (0.03 mol) of piperazine hexahydrate, and 5.7 grams (0.03 mol) of p-toluenesulfonyl chloride were condensed by the same procedure .as outlined in Example 3. When cool. the product was a dark brown wax.

Examlple 6.--A mixture of 3.7 grams (0.019 mol) of piperazine hexahydrate and'6.5 grams (0.019 mol) of erucic acid was heated carefully to expel water and then stirred at 150-160 C. for 2.5 hours. When cool, the product was a clear, brown waxy material. 7 a

The products hereinabove described, while not ordinarily considered as soluble in water to any great extent, may be suitably dispersed in water or emulsified therewith, so that effective amounts thereof may be introduced and be present in the water within the steam generator under operating conditions. The emulsifying or dispersing agent used must, however, be of a kind that does not cause foaming, either by itself or by its decompoper gallon'of this type of condensation product will suppress foam in a boiler for from 15 to 20 minutes. Comparing this with the efllcacy of castor oil used on the order of M grain per gallon, which will suppress the foam for only about 30 seconds to one minute, it is obvious that if one were to use castor oil it would have to be almost continuously fed into the boiler, with the unavoidable accumulation in the boiler of a lot of soap produced by the reaction of the liberated fatty acids with the alkali present in the water, which would only aggravate the problem. The acyl Gallon and even less can be used. The process is particularly effective at pressures of about pounds per square inch. v

The introduction of the antifoaming compounds of the present invention into the boiler may be accomplished in a number of ways. Thus,

the antifoaming compositions may be dispersed or physically mixed with, say, sodium carbonate I orsome other material used for treating the boiler water and pumped with the feed water into the boiler by means of either an injector or a feed water pump. The compounds may also be dissolved in suitable organic water-miscible solvents such as alcqhols, ethers, ketones, etc. and introduced in small measured amounts into the feed water entering the boiler. chanical measuring devices which will periodically or continuously inject the required dosage may be used, so that the introduction will be more or less in proportion to the steam consumption to which the steam generator is subjected. Another manner of introducing the antifoaming compounds is to form an emulsion thereof in water and then feed said emulsion either directly into the boiler or the. feed water lines leading to it. The invention therefore is not to be limited by the manner of introduction of the -,antifoaming composition but rather is to be construed in the terms of the hereunto appended solids tending to prdduce foaming and priming Suitable meof the 'antifoaming compounds into the feed water. V

a quantity of a high-molecular-weight monoacyi derivative of piperazine sufficient to substantially inhibit priming and foaming, said derivative coni taining at least about 24 carbon atoms.

2. Process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amount of tbtal solids tending to produce foaming and priming a quantity of a fatty acid diacyl derivative of piperazine suflicient to substantially inhibit priming and foaming, said derivative containing at least about 34 carbon atoms where the acyl groups are substantially equal and at least about 22 carbon atoms where the radicals are widely different.

3. Process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a quantity of a diacyl derivative of piperazine, at least one acyl group being derived from the group consisting of the aromatic carboxylic and aryisulfonic acids, and the other acyl group containing at least about 16 carbon atoms, said quantity of diacyl derivative being suflicient to substantially inhibit priming and foaming.

.4. Process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric'pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a quantity of dipalmitylpiperazine', said quantity being sufficient to substantially inhibit priming and foaming.-

5. Process of minimizing the production of foam in and the priming of steam generators operating under superatmospheri'c pressure conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming a quantity of acetylstearylpiperazine, said quantity being suflicient to substantially inhibit priming and foaming.

6; Process of minimizing the production of foam in and the priming of steam generators operating under superatmospheric pressure. conditions which comprises incorporating with a water therein containing an amount of total solids tending to produce foaming and priming afquantity of monoerucylpiperazine, said quanmy being sufficient to substantially inhibit prim-' ing and foaming.

ARTHUR L. JACOBY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,074,380 Fiett Mar. 22, 1937 1,892,857 Spellmeyer Jan. 8, 1933 2,262,357 De Groote et a1. Nov. 11, 1941 2,304,805 Denman Dec. 15, 1942 2,328,551

Gunderson Sept. 7, 1943 

